According to the United States Census Bureau, the city has a total area of 43.5 km² (16.8 mi²). 40.4 km² (15.6 mi²) of it is land and 3.1 km² (1.2 mi²) of it is water. The total area is 7.03% water.
As of the census of 2000, there are 20,784 people, 9,875 households, and 4,858 families residing in the city. The population density is 514.1/km² (1,331.3/mi²). There are 10,186 housing units at an average density of 251.9/km² (652.5/mi²). The racial makeup of the city is 93.55% White, 2.13% African American, 0.21% Native American, 2.44% Asian, 0.02% Pacific Islander, 0.28% from other races, and 1.36% from two or more races. 1.35% of the population are Hispanic or Latino of any race.
There are 9,875 households out of which 20.0% have children under the age of 18 living with them, 37.8% are married couples living together, 8.6% have a female householder with no husband present, and 50.8% are non-families. 38.9% of all households are made up of individuals and 11.5% have someone living alone who is 65 years of age or older. The average household size is 2.04 and the average family size is 2.75.
In the city the population is spread out with 17.2% under the age of 18, 7.2% from 18 to 24, 36.2% from 25 to 44, 23.2% from 45 to 64, and 16.3% who are 65 years of age or older. The median age is 38 years. For every 100 females there are 94.5 males. For every 100 females age 18 and over, there are 92.0 males.
The median income for a household in the city is $45,195, and the median income for a family is $59,630. Males have a median income of $41,966 versus $29,024 for females. The per capita income for the city is $27,540. 9.3% of the population and 6.4% of families are below the poverty line. Out of the total people living in poverty, 14.3% are under the age of 18 and 8.4% are 65 or older.